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    Weather station reports. True or magnetic

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    • ivo
      ivo Administrator last edited by

      Question to all wind gurus here

      Weather stations wmo and madis report their wind direction in true or magnetic?

      1 Reply Last reply Reply Quote 0
      • G
        GiovanniV last edited by

        Wind direction is defined as the direction from which the wind blows, and is measured clockwise from geographical north, namely, true north (based on the World Geodetic System 1984 (WGS-84) and its Earth Geodetic Model 1996 (EGM96)). - source: WMO

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        • ivo
          ivo Administrator last edited by

          Even in METARs? I guess METARs use magnetic.

          Gkikas LGPZ R 3 Replies Last reply Reply Quote 0
          • Gkikas LGPZ
            Gkikas LGPZ Moderator @ivo last edited by

            @ivo
            I copy from https://www.faa.gov/air_traffic/publications/media/aim.pdf
            Chapter 7, section 1
            53f543bf-c994-49e8-a343-dc3784810a00-εικόνα.png

            1 Reply Last reply Reply Quote 3
            • G
              GiovanniV last edited by

              I am not familiar with weather reports in the flight sector but according to German weather service (DWD) it is reported in true north(German source: DWD).

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              • Gkikas LGPZ
                Gkikas LGPZ Moderator @ivo last edited by

                @ivo
                Maybe you refer to:
                If you read it (METAR), it's true. If you hear it (ATIS), it's magnetic.

                All charts and textual sources (METAR, TAF, winds aloft, surface analysis charts, etc) use true north as the reference.

                ATIS/AWOS/ASOS broadcasts, or any information a controller gives you over the radio, is magnetic.

                See:International Airport Example 1,
                here https://en.wikipedia.org/wiki/Automatic_terminal_information_service

                Gkikas LGPZ 1 Reply Last reply Reply Quote 1
                • Gkikas LGPZ
                  Gkikas LGPZ Moderator @Gkikas LGPZ last edited by Gkikas LGPZ

                  @ivo
                  As the magnetic declination in Czech Rep. is 3~5 degrees and wind direction is given in tens of degrees, you have no problem!
                  But if you fly to Greenland ....
                  https://screenshots.firefox.com/kCNSJ4D19uIqOUNs/upload.wikimedia.org
                  the ATC will give you wind dir. (for landing) in magnetic
                  (also runways names (01 up to 36), refer to magnetic azimuth in tens of degrees).

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                  • robertocosquin
                    robertocosquin last edited by

                    No problem

                    Roberto Mario Ramirez

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                    • csabatatar
                      csabatatar Moderator Pilot last edited by

                      @ivo
                      I totally agree with @Gkikas-LGPZ .
                      The best mnemonic for it is: WRITTEN --> TRUE; SPOKEN --> MAGNETIC.

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                      • R
                        regetr Meteorologist @ivo last edited by

                        @ivo

                        from ICAO annex 3/chapter 4;

                        metar.PNG

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